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CVE-2026-49455: Waku: Cross-Origin CSRF on RSC Server Action Dispatch

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-03 · updated 2026-09-09
• Weakness: CWE-352

Description

Waku is the minimal React framework. Prior to version 1.0.0-beta.1, Waku's RSC request dispatcher invokes server actions without validating the request's Origin (or Sec-Fetch-Site) header. A cross-origin web attacker can therefore cause a victim browser to issue an authenticated POST to a registered server action endpoint using a CORS-safelisted content type (text/plain), which does not trigger a preflight. Any state-mutating server action that the application exposes via 'use server' can be invoked with the victim's cookies attached. This issue has been patched in version 1.0.0-beta.1.

Affected products

• wakujs waku: before 1.0.0-beta.1

References

• https://github.com/wakujs/waku/releases/tag/v1.0.0-beta.1
• https://github.com/wakujs/waku/security/advisories/GHSA-75w3-gmqx-993q

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